1. Field of the Invention
The present invention relates to an image recording apparatus which uses a multi-channel light modulator, more specifically calibration of the beam intensity.
2. Description of the Background Art
Use of a multi-channel light modulator well known in the art of image recording. Such a light modulator is illuminated by light from a light source and creates multiple writing beams. To ensure high image quality, each writing beam is required to have a same target intensity. A conventional method for this purpose is to calibrate all writing beams in accordance with signals from a single-element photodetector.
If a multi-channel light modulator has a low extinction rate(contrast), however, a signal from a single-element photodetector can be lost in the noise generated by light from unselected modulator elements. Provided a modulator has 500 elements with a contrast of 100:1, total beam intensity of the unselected 499 elements is about five times the intensity of a selected element. The purpose of this invention is to overcome this difficulty.